When changing powder colors in an electrostatic powder coating-system, the powder-carrying connecting lines, the spray compartment, the powder containers and the spray guns must be thoroughly cleaned. Using presently known methods and apparatus, it is particularly difficult to clean powder hoses. By contrast to cleaning the compartments or containers (which may be manually cleaned with brooms, or automatically cleaned with moving brush and blower systems), powder hoses have up to now been relatively unsatisfactorily cleaned by blowing compressed air therethrough. The new powder color must then be first sprayed "into the open air", to ensure that all of the residual powder has passed out of the hoses. Such practice is both unreliable and uneconomical. It is therefore standard practice to replace the powder hoses between each color change, so that a separate hose is provided for every color. Replacing hoses can be complicated and time-consuming, particularly with frequent color changes. In automated or robotic systems, hose replacement is particularly problematic, since the hoses must be re-secured to the points of articulation of the mobile spray gun mounting structure.